Equity - Restricted Retained Earnings and Other (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Restricted Retained Earnings
Undistributed earnings of TCF's bank subsidiary	$ 170,200,000
Amount of provision for federal income taxes related to undistributed earnings of TCF's bank subsidiary	0
Other
Shares held in trust for deferred compensation plans, at cost	26,731,000	$ 28,037,000
Repurchases of common stock	33,098,000	86,309,000	$ 212,929,000
Aggregate value remaining in the stock repurchase program	89,400,000
Treasury stock reissued	$ 0	$ 12,900,000	$ 378,000
Treasury stock reissued (in shares)		347,329	8,130
Legacy TCF
Other
Repurchases of common stock		$ 58,800,000	$ 212,900,000